What is wrong with this vacuum scenario ?

[Externet]

Hi.

Torricelli's barometer is water in a tube, 34 ft (10.4 m) tall column.

 

The space above the water surface in the tube is vacuum.

 

Isn't the water surface supposed to boil at room temperature under that extreme vacuum ?

 

What about the rest of the water column... progressively less boiling with depth ?

 

And does that boiling water fill the vacuum space with vapor becoming no vacuum any more ? Then what? If vacuum is not perfect anymore, the water column starts decreasing its height?

 

Miguel

[swansont]

You'll get the vapor pressure of water - it's a relative vacuum, i.e. it's at low pressure.

[Externet]

Hi.

If it was a mercury column instead of water, then the vacuum chamber will contain mercury vapor.

Is the 760mm of Hg actually the barometric pressure minus the Hg vapor pressure at that temperature?

If yes, the atmospheric pressure standard of 760mm is a wrong figure because of the unacounted Hg vapor. The real figure should be higher !

 

In other words, the barometric standard changes with the Hg temperature ¿?

 

Now, to some misconceptions... I do not have it clear... the void is not really total vacuum as I thought, and the standard is not ?

If the liquid in the column was some very special fluid not releasing any of its vapor at all, would there ever be a void above it?

 

And to make things harder; would a suction piston move effortlessly attempting to expand vacuum in outer space? Can a volume of nothing be expanded to a larger volume of nothing ?

 

Miguel